1. Field of the Invention
The present invention relates in general to an atom collimator such as used for collimating atoms in forming of a metal contact in a contact hole of a semiconductor substrate and, more particularly, to an atom collimator having a square configuration and a curved surface with a radius of curvature.
2. Description of the Prior Art
Typical atom collimator used for collimation of atoms in a deposition forming of contacts of semiconductor device has a hexagonal honeycomb-type configuration in order to provide the same condition for all the sections of a semiconductor substrate such as a silicon substrate, This typical hexagonal collimator allows specifically oriented atoms to be received by a contact hole of the silicon substrate during a physical vapor deposition (PVD) for forming the contact, such as a metal contact, in the contact hole of the silicon substrate. In this regard, the typical hexagonal collimator achieves no desired good step coverage and no homogeneity of the semiconductor device,
FIG. 1 is a view showing the typical hexagonal collimator placed above a wafer formed with a die, and FIG. 2 is a partially enlarged view showing a positional relation between the above typical collimator and a contact hole of the die. In these drawings, the reference numerals 1, 2 and 3 denote the collimator, the die and the contact hole of the die, respectively.
As shown in these drawings, the typical collimator I has a hexagonal configuration in order to provide the same condition for all the sections of the wafer. Hence, the hexagonal collimator displaced above a specified sections of the wafer such that it is placed above the contact hole 3 of the die 2.
As shown in FIG. 2, since the collimator I is placed above the contact hole 3 of the die 2, vertically advancing atoms is blocked by the collimator 1 and not received by the contact hole 3 while atoms advancing with inclined angles of incidence are received by the contact hole 3 in order to form the contact in the contact hole 3.
Hence, it will be noted that the atoms are unevenly received by the contact hole when the hexagonal collimator 1 is placed above the contact hole 3 while there is no problem when the collimator I is placed diverging from the contact hole 3. That is, the conventional hexagonal collimator 1 has a problem that when it is placed above a specified contact hole 3 as shown in FIG. 2, it blocks the vertically advancing atoms but allows the atoms advancing with inclined angles of incidence to be received by the contact hole 3, thus to achieve no desired good step coverage and no homogeneity of the contact hole 3.